Imagine walking through a supermarket. You’re in the fruit aisle deciding which of them will make the cut and which of them won’t. Say you’re looking for mangoes, a number of factors influence your decision, but the ability to feel and gauge the ripeness of a mango is ineffable.
Many of us have thought of touch more often than usual since the pandemic began. Hugs and high fives outside of our immediate household are rare to come by these days. Being unable to go anywhere has meant not feeling the grass under our toes, or being submerged underwater in a pool. Touch is vital to all of us.
Scientists have been working on haptics since the 1960s. It is important to understand what this is, and what this technology could mean for the future. A haptic interface is a feedback device that generates sensation in the skin and muscles, including a sense of touch, weight and rigidity. However, compared to ordinary visual and auditory sensations, haptics is far more difficult to synthesise. It’s unlike vision, which is communicated virtually with cameras and monitors, or hearing, where sounds can be relayed to our ears with speakers.
“Anytime we touch anything, our perceptual experience is the product of the activity of thousands of nerve fibers and millions of neurons in the brain,” says Sliman Bensmaia, a neuroscientist at the University of Chicago. The body’s natural sense of touch is remarkably complex. Nerve receptors detect cues about pressure, shape, motion, texture, temperature and more. Those cues cause patterns of neural activity which the central nervous system interprets so we can tell if something is smooth or rough, wet or dry, moving or still.
What does the development of this technology mean for us? In the short term, people who have lost limbs or are paralysed may recover some sense of touch through their artificial limbs. It will expand the world of virtual reality and enable new forms of remote medicine. In the long term, we’d be able to feel while shopping online!
How it’s done is a long and complicated process, but I’ll break it down for you. One of the goals for haptics researchers is to mimic sensations resulting from force and movement such as pressure, sliding or rubbing. “Anytime you’re interacting with an object, your skin deforms,” or squishes a bit, Bensmaia explains. Press on the raised dots of a braille letter, and the dots will poke your skin. Rub fabric between your fingers and the action produces vibrations. Four main types of touch receptors respond to mechanical stimulation of the skin: Meissner corpuscles, Merkel cells, Ruffini endings and Pacinian corpuscles. Pacinian corpuscles sit deep in the skin. They are especially good at detecting vibrations created when we interact with different textures. It’s similar to the way we hear a series of notes and recognize a tune.
“Corduroy will produce one set of vibrations. Organza will produce another set,” Bensmaia says. Each texture produces “a different set of vibrations in your skin that we can measure.” Such measurements are a step towards trying to reproduce the feel of different textures. Another important point to note is that these stimuli meant to mimic a particular sensation must be strong enough to trigger responses. Each vibration creates a different kind of wave energy. Researchers from the University of Birmingham found that rolling-type waves called Rayleigh waves go deep enough to the Pacinian receptors. This level varies between different mammals.
So ideally, in the long run, if you’re shopping on Amazon, you could feel fabric. Web pages’ computer codes would make certain areas on a screen mimic different textures, with shifts in electrical charge, vibration signals, ultrasoundor other methods. This could be a game changer.